This application claims the benefit of Korean Application No. 2002-33222, filed Jun. 14, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to an air conditioning apparatus and control method thereof, which has a pulse with modulation compressor and a two-stage variable-capacity compressor.
2. Description of the Related Art
Generally, a single air conditioning apparatus in which one indoor unit is connected to one outdoor unit does not have a large indoor air conditioning load (required capacity), so a fixed-capacity compressor is installed in the outdoor unit.
On the contrary, a multi-unit air conditioning apparatus in which a plurality of indoor units are connected to one outdoor unit is designed such that each of the indoor units independently copes with an air conditioning load of a corresponding indoor space. In such a multi-unit air conditioning apparatus, since air conditioning loads of respect indoor units are different and vary at any time, a variable-capacity compressor is installed in an outdoor unit, and a flow of refrigerant is controlled by ascertaining loads and operating states using communication between each of the indoor units and the outdoor unit. Further, the variable-capacity compressor is controlled by a microcomputer of the outdoor unit. The outdoor unit microcomputer checks the air conditioning requirements with respect to a corresponding indoor space, a temperature condition of the corresponding indoor space, etc. based on information received from each of the indoor units, and controls a capacity of the compressor according to the checked information.
However, since a conventional multi-unit air conditioning apparatus employs a construction in which a plurality of indoor units are connected to one outdoor unit, a compressor installed in the outdoor unit must be designed to endure a maximum indoor air conditioning load. Further, in order for a compressor to endure the maximum indoor air conditioning load, a significant difficulty arises in the production of the compressor. That is, a plurality of performance tests must be carried out so as to increase the capacity of the compressor.
A high-capacity compressor produced by the above process is problematic in that the high-capacity compressor is very expensive, relative to a conventional compressor.
A manner in which a variable-capacity compressor and a fixed-capacity compressor are mixed to cope with indoor air conditioning loads is used in consideration of the above problem.
As shown in FIG. 1, a variable-capacity compressor 10, which operates at a capacity that is varied according to a frequency of an inverter circuit and a fixed-capacity compressor 20 which operates at a constant capacity are connected in parallel with each other. Further, an outdoor unit microcomputer controls capacities of the variable-capacity compressor 10 and the fixed-capacity compressor 20 according to indoor air conditioning loads (required capacities) received from respective indoor units. Referring to FIG. 2, if the indoor air conditioning loads are 0 to 50%, the outdoor unit microcomputer controls the capacity of the variable-capacity compressor 10. In this case, the microcomputer controls the capacity of the variable-capacity compressor 10 by varying a frequency outputted to the variable-capacity compressor 10 from an inverter circuit within a predetermined range R1 according to the indoor air conditioning loads (required capacities) received from the respect indoor units. Further, if the indoor air conditioning loads are 50 to 100%, the outdoor unit microcomputer controls the capacities of the variable-capacity compressor 10 and the fixed-capacity compressor 20. In this case, the microcomputer copes with an insufficient capacity by controlling the capacity of an inverter-type variable-capacity compressor 10 operated according to frequency of the inverter circuit within a predetermined range R2 after activating the fixed capacity compressor 20.
However, if the conventional air conditioning apparatus is used for facilities such as large buildings, a capacity, which must be provided by a variable-capacity compressor, inevitably becomes large. Further, to produce such a high-capacity compressor as an independent device is difficult and expensive, even though an independent device can be produced, thus causing an economic burden by increasing a price of the compressor.
Therefore, in the multi-unit air conditioning apparatus, a method is required of effectively coping with a large-scale indoor air conditioning load (required capacity). Further, a method of accommodating requirements for the large-scale air conditioning capacity while using a conventional compressor is seriously required.
Accordingly, an air conditioning apparatus and control method thereof is provided, in which a pulse width modulation compressor and a two-stage variable-capacity compressor are connected in parallel with each other to cope with indoor air conditioning loads, thus realizing the compressors at a low price.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to accomplish the above and other aspects an air conditioning apparatus is provided, comprising a first compressor controlled in a pulse width modulation manner; a second compressor connected in parallel with the first compressor and controlled to operate at one of a minimum capacity and a maximum capacity; and a control unit controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to indoor air conditioning loads.
Further, an air conditioning apparatus is provided, comprising a plurality of indoor units; and an outdoor unit connected to the plurality of indoor units comprising a first compressor controlled in a pulse width modulation manner; a second compressor connected in parallel with the first compressor and controlled to operate at one of a minimum capacity and a maximum capacity, and an outdoor control unit controlling the capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to indoor air conditioning loads required by the indoor units.
Further, a method of controlling an air conditioning apparatus is provided, the air conditioning apparatus having a plurality of indoor units connected to an outdoor unit comprising a first compressor controlling a capacity of the outdoor unit in a pulse width modulation manner and a second compressor operating at one of a minimum capacity and a maximum capacity, comprising calculating an air conditioning capacity required by corresponding indoor units; and controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to the calculated air conditioning capacity, wherein a maximum capacity of the first compressor is equal to the minimum capacity of the second compressor, and the maximum capacity of the second compressor is twice the minimum capacity of the second compressor.
An embodiment of the present invention uses two compressors connected in parallel with each other, and controls capacities of the two compressors similarly to an operation of controlling a capacity of a single large-capacity compressor. One of the compressors is a pulse width modulation compressor which linearly controls the capacity of the pulse width modulation compressor, and another compressor is a two-stage variable-capacity compressor which has a relatively large capacity and operates at two different capacities.